The present technology relates to an electrophoretic element including an electrophoretic particle and a porous layer, a display using the electrophoretic element, and an electronic device using the display.
In recent years, with the popularization of various electronic devices such as cell-phones and personal digital assistants (PDAs), the demand for a display having low power consumption and high-definition image quality has increased. Specifically, recently, with launch of an electronic book distribution service, an electronic book reader for reading, which has an intention of reading character information for a long time, has attracted attention, and it is desirable to produce a display having a suitable display quality for the application.
Displays for reading such as a cholesteric liquid crystal display, an electrophoresis display, an electrochromic display, and a twist ball type display have been proposed, and specifically preferred is that classified as a reflection type. Since the reflection type display employs the reflection (scattering) of outside light like paper to provide light display, paper-like display quality is obtainable. Additionally, there is no need to prepare a backlight, and power consumption then decreases.
A candidate of the reflection type displays is an electrophoretic display creating light and dark (contrast) using an electrophoretic phenomenon, since the power consumption is low and high-speed response is excellent in the electrophoresis display. Then, various studies have been made on a display method of the electrophoretic display.
Particularly, there is a proposed method of dispersing two kinds of charged particles having different optical reflection characteristics and different polarities in an insulating liquid to cause the movement of each charged particle using the difference in polarity in response to an electric field (for example, see Japanese Exampled Patent Application Publication No. 50-015115 and Japanese Patent No. 4188091). In this method, the distribution of two kinds of charged particles changes in response to an electric field, and contrast is then created with use of a difference in optical reflection characteristics between the charged particles.
There is also a proposed method of dispersing charged particles in an insulating liquid and also arranging a porous layer having different optical reflection characteristics from those of the charged particles to cause the movement of the charged-particles passing through fine pores of the porous layer in response to an electric field (for example, see Japanese Unexamined Patent Application Publication Nos. 2005-107146, 2005-128143, and 2002-244163, and Japanese Examined Patent Application No. 50-015120). As the porous layer, a polymer film having fine pores formed by a drilling process using a laser beam, a knitted fabric made from synthetic fiber, an open-cell porous polymer, or the like is used. In the method, the distribution of charged particles changes in response to an electric field, and contrast is created with use of a difference in optical reflection characteristics.